since in this specific case (r == 0) `errno` is irrelevant and most likely
set to zero, leading up to a confusing message:
```
[ 120.595085] H systemd[1]: session-5.scope: No PIDs left to attach to the scope's control group, refusing: Success
[ 120.595144] H systemd[1]: session-5.scope: Failed with result 'resources'.
```
Currently, if journald coredumps, the coredump is written to
/var/lib/systemd/coredump but the coredump metadata is not written
to the journal meaning we can't find out about the coredump's
existence via the journal. This means that coredumpctl can't be
used to work with journald coredumps, as well as any other tools
that rely on journald to know about coredumps.
To solve the issue, let's have systemd-coredump try to write
systemd-journald coredump metadata to the journal. We have to be
careful though, since if journald coredumps, there's no active
reader on the receive end of the journal socket, so we have to make
sure we don't deadlock trying to write to the socket. To avoid the
deadlock, we put the socket in nonblocking mode before trying to
write to it.
When chase_symlinks() is called on something on a doesn't exist, it immediately
returns an error. But we were relying on it to prepend "/sysroot/". If it
fails, we need to do that ourselves.
For example, with /sysroot/etc/fstab containing a line for /foo, if /sysroot/foo
doesn't exist, we'd generate a mount point for /foo.
Originally (6b1dc2bd3c) we had 'pre' and 'post'
to refer to remote-fs-pre.target and remote-fs.target or local-fs-pre.target
and local-fs.target. But 'pre' is long gone, and 'post' by itself doesn't
make much sense. Rename it for clarity.
Mount information can come from /etc/fstab, /sysroot/etc/fstab, and
/proc/cmdline. Even when we had the path to the right source handy, we would
often write something inaccurate. In particular, in the initrd, we would
generally write "/etc/fstab" instead of "/sysroot/etc/fstab" for no good
reason.
We would always print output to the kmsg or journal, but that is only needed
and useful when invoked by systemd. So let's skip redirection unless we are
invoked by systemd. Otherwise, let's log normally. This makes test invocations
easier, and also helps when the generator is invoked by mistake. If redirection
is necessary, the generator can be invoked with SYSTEMD_LOG_TARGET=… even
during tests.
Ambient capabilities should not be passed implicitly to user
services. Dropping them does not affect the permitted and effective sets
which are important for the manager itself to operate.
Inspired by https://github.com/systemd/systemd/pull/24024 this is
another user mode helper, where this might be an issue. hence let's
rather be safe than sorry, and also connect stdin/stdout/stderr
explicitly with /dev/null.
Since the general generator logic was established in the rewrite in
07719a21b6, generators would always write to /tmp
by default. I think this not a good default at all, because generators write a
bunch of files and would create a mess in /tmp. And for debugging, one
generally needs to remove all the files in the output directory, because
generators will complain in the output paths are already present. Thus the
approach of disabling console logging and writing many files to /tmp when
invoked with no arguments is not nice, so let's disallow operation with no
args.
But when debugging, one generally does not care about the separate output dirs
(most generators use only one). Thus the general pattern I use is something
like:
rm -rf /tmp/x && mkdir /tmp/x && build/some-generator /tmp/{x,x,x}
This commit allows only one directory to be specified and simplifies this to:
rm -rf /tmp/x && mkdir /tmp/x && build/some-generator /tmp/x
This is useful to use "f" or "w" to write arbitrary binary files to
disk, or files with newlines and similar (for example to provision SSH
host keys and similar).
When invoked as the coredump handler by the kernel, systemd-coredump's
stdout and stderr streams are closed. This is dangerous as this means
the fd's can get reallocated, leading to hard to debug errors such as
log messages ending up being appended to a compressed coredump file.
To avoid such issues in the future, let's bind stdout/stderr to
/dev/null so the file descriptors can't get used for anything else.
This imports credentials also via SMBIOS' "OEM vendor string" section,
similar to the existing import logic from fw_cfg.
Functionality-wise this is very similar to the existing fw_cfg logic,
both of which are easily settable on the qemu command line.
Pros and cons of each:
SMBIOS OEM vendor strings:
- pro: fast, because memory mapped
- pro: somewhat VMM independent, at least in theory
- pro: qemu upstream sees this as the future
- pro: no additional kernel module needed
- con: strings only, thus binary data is base64 encoded
fw_cfg:
- pro: has been supported for longer in qemu
- pro: supports binary data
- con: slow, because IO port based
- con: only qemu
- con: requires qemu_fw_cfg.ko kernel module
- con: qemu upstream sees this as legacy
This can be useful for users of slow block devices.
For example, the persistent-storage rules are needed for USB floppy
drives be recognized by udisks2, but the extra blkid calls cause
thrashing for 25+ seconds after every disk change.
With this change, a user wishing to avoid the extra blkid invocation(s)
could create /etc/udev/rules.d/55-floppy-noprobe.rules as follows:
# Don't probe PC floppy drives
SUBSYSTEM=="block", KERNEL=="fd*", \
ENV{UDEV_DISABLE_PERSISTENT_STORAGE_BLKID_FLAG}="1"
# Don't probe USB floppy drives
SUBSYSTEM=="block", SUBSYSTEMS=="usb", \
ATTRS{bInterfaceClass}=="08", ATTRS{bInterfaceSubClass}=="04", \
ENV{UDEV_DISABLE_PERSISTENT_STORAGE_BLKID_FLAG}="1"
I didn't exclude floppies by default in this change, because floppy
devices are also emulated by some BIOSes/hypervisors in some cases, and
I don't know how many systems would fail to boot if /dev/disk/by-uuid/*
became unavailable for 'floppy disks' on those systems.
Daan De Meyer
David Tardon
Vito Caputo
Frantisek Sumsal
Yu Watanabe
Lennart Poettering
lastkrick
Zbigniew Jędrzejewski-Szmek
Łukasz Stelmach
Darsey Litzenberger